Sound output control for telephone ringers



June 23, 1959 H. A. BREDEHOFT 2,392,187

SOUND OUTPUT CONTROL FOR TELEPHONE RINGERS Filed oci. 1e. 1952 PEHMANE NT MA CNE T PE RMANE N T' MAG/JE T /NVENTOR H. A. BREDEHOFT ATTORNEYUnited States Patent SOUND OUTPUT CONTROL FOR TELEPHONE RINGERS HaroldA. Bredehoft, Millington, NJ., assignor to Bell Telephone Laboratories,Incorporated, New York, N.Y., a corporation of New York ApplicationOctober 16, 1952, Serial No. 314,996

2 Claims. (Cl. 340-397) This invention relates to audible signalingdevices of the percussion type and particularly to sound regulators foruse in controlling the sound output of telephone ringers.

The telephone ringer in common usage includes a pair of gongs and anelectromagnetically controlled clapper suitably mounted and disposedrelative thereto for striking the gongs. The intensity of the soundsignal emitted by signaling devices of the percussion type, andparticularly by the telephone ringer, is known to be a measure of theenergy with which the gong is struck by the clapper which, in turn, isdetermined to some degree by the stroke of the ringer armature whichcontrols the movement of the clapper.

Attempts have been made heretofore to provide subscriber-controlledmeans for regulating the sound output of the telephone ringer and, ingeneral, such attempts involve arrangements which require adjusting thespacing between gongs and, in some cases, adjusting the armature strokein accordance with the gong spacing. While such devices functionsatisfactorily, they necessitate more or less complicated mechanisms formoving the gongs, which mechanisms contribute to the cost of the ringerand require additional maintenance.

It is the object of this invention to provide a simple, practicable andotherwise improved system of sound control for telephone lingers whichobviates the need for adjustable armature stops and/or relativelymovable gongs, and which is particularly adaptable to subscriberoperation.

This object is attained in accordance with a feature of the invention bypivotally mounting the clapper rod on the electromagnetically controlledarmature and adjustably controlling the energy transmitted from thearmature to the clapper 'through the medium of a variable couplingbetween the clapper rod and the armature, the strength of which may bevaried, at will, by the subscriber.

More particularly, and in accordance with one embodiment of theinvention, the clapper rod is pivotally mounted on the ringer armatureata point intermediate its (the rods) extremitiesv and, through the mediumof a variably tensionable spring, a force is applied to one end of theclapper rod, the line of application of which coincides with thelongitudinal axis ofthe clapper rod and passes through the `pivot pointthereof. Manually operable means is made available to the subscriber foradjusting the spring tension so that when the tension is low there willbe little energy transmitted to the gongs by the armature and as thetension is increased the coupling is increased and the gongs are struckwith greater force and the sound output is correspondingly increased.

In a second embodiment of the invention, the clapper assembly or supportconsists of two magnetically coupled sections, one of which is xed tothe ringer armature and the other is pivotally mounted thereon. The tworod sections are in alignment and their juxtaposed ends terminate inmagnetic iron pole-pieces effecting an air-gap;

frice a permanent magnet is manually positioned variably with respect tothe pole-pieces or iron details to vary the magnetic flux in the air-gapand to correspondingly control the strength of the coupling. As thepermanent magnet is brought closer to the iron details or pole-piecesthe flux in the air-gap increases, causing an increase in the couplingbetween the clapper rod and the armature and therefore in the ability ofthe armature to transmit energy to the ringer gongs. Conversely, as thedistance between the permanent magnet and the pole-pieces increases, theair-gap llux decreases and the clapper rod-armature coupling decreasescausing less energy to be transmitted from the armature to the gongs anda corresponding sound signal of less intensity.

The invention will be better understood from the following detaileddescription when read with reference to the accompanying drawings, inwhich:

Figs. l and 2 are front and side views, respectively, of a telephoneringer which includes that embodiment of the invention wherein thecoupling between armature and clapper rod is stiffness controlled bytensioning means; Fig. 3 is a side view of a telephone ringer whichincludes that embodiment of the invention wherein the coupling betweenthe armature and clapper rod is stiffness controlled by magnetic means;and

Fig. 4 is a fragmentary perspective view of the ringer disclosed in Fig.3 and illustrates, particularly, the elements of the armature-c-lappercoupling involved therein.

In the several drawing figures the invention is disclosed as embodied ina ringer structure of the type disclosed in H. A. Bredehoft and M. S.Richardson Patent 2,590,500 of March 25, 1952, and includes anirregularly-shaped frame, which may be die-cast of aluminum, or of anyother suitable material, having a central post 12, two substantiallyparallel arms 15 and 16 projecting at right angles from the upper andlower ends, respectively, of the post 12 and a pair of integrally formedgong posts 13 and 14 on each of which is suitably mounted a gong, suchas gongs 17 and 18, respectively.

A unit-type pole-piece 20 is xed to the frame arms 15 and 16 by means ofself rivets 19. The pole-piece element is disclosed more clearly in Fig.4 of the drawings of the above-identified Bredehoft-Richardson patent.It terminates in extremities 21 and 22 which are so relatively disposedas to dene an air-gap in which an armature 23 is adapted to vibrateunder the joint control of the magnet coil 24 and a small cylindricalpermanent magnet 25. The armature 23 is mounted on a bracket 9 by meansof a spring hinge 8, the bracket being secured to the frame in anysuitable manner and the hinge 8 to the bracket and armature preferablyby rivets.

The coil 24 is mounted on a laminated core structure which, togetherwith a silicon steel shunt 27, is secured to the frame pieces 15 and 16by screws 28.

The vstructure thus far described constitutes essentially the magneticand electrical elements of the ringer and forms no part of the presentinvention. The aboveidentied Bredehoft-Richardson patent contains a fulldescription of these elements and their interrelationship, whichdescription need not be repeated here.

The clapper rod 30, which supports the clapper 31 at its upper end, ispivotally mounted on a relatively stiff rod 32 (Fig. 2) which is stakedto the armature 23 at its (the armatures) upper end. A suitable pivotbear ing is indicated at 33. The lower lend of the clapper rod 30 isformed to accommodate, in fixed relation, one end of a coil spring 34the other end of which has fixed thereto one end of a cord 35 of silk orother suitable material. The cord 35 has its other end wound around -ashaft or trunnion 36 which is housed in a cylindrical sleeve formedintegral with the frame. A thumb wheel 37 is xed to the outer end of thetrunnion 36 by means of a screw 38 and provides means for manuallyrotating the trunnion to vary the pull on the cord 35 and tocorrespondingly vary the tension of spring 34. The shank of thumb wheel37 is provided with a series of small closely spaced cavities orindentations which cooperate with -a stop 39 in maintaining the trunnionin any position to which it may be rotated. The stop 39 is fixed to theframe by means of a screw 40.

lWhen the tension in the cord 35 is low, little energy is transmitted tothe gongs by the armature 23 incident to the latters vibratory actionwhich results from the energization of coil 24 by ringing current.Consequently, the gongs 17 and 18 will be struck relatively weak blowsby the clapper 31 and the resulting sound signals will be of relativelylow intensities. When the trunnion 36 is turned counterclockwise(Fig. 1) by the thumb wheel 37 to increase the tension in spring 34 andcord 35, the coupling between the armature and clapper rod will bestrengthened and the gongs will be struck more powerful blows resultingin a greater sound output from the ringer.

It is to be noted that in tensioning the cord 35 a variable force isapplied to the clapper rod 30 in a direction parallel to thelongitudinal axis thereof and on -a line which passes through the pivotpoint 33. When the tension is light the elastic coupling of clapper rod30 to the armature extension 32 is one of very low stiffness and anyincrease in this tension increases the stiffness of the coupling andtherefore enables more energy to be transmitted to the gongs by ythearmature.

With reference to Figs. 3 and 4 it will be observed that, except for theelements involved in the sound regu# lator of the embodiment of theinvention disclosed theref in, the ringer structure disclosed issubstantially identical to that of Figs. l and 2. Similar parts of thetwo groups of figures therefor are given the same designations and thedescription thereof heretofore made with reference to Figs. 1 and 2applies equally well to Figs. 3 and 4 and will not be repeated.

The clapper rod 40 supports the clapper 31 at its (the rods) upperextremity and is pivotally mounted at 41 to an armature extension rod 42which is staked or other-j wise fixed to the armature 23 as shown. Thelower end of the clapper rod 40 terminates in a magnetic iron polepiece43. A second pole-piece 45 is rigidly supported on armature 23 by therod 44 in such a position that the pole-pieces 43 'and 45 occupy thesame plane. The polepieces 43 and 45 are semiannular discs havingjuxtaposed serrated edges which are in such close proximity as to eect asmall air-gap.

A permanent magnet 46, which is substantially U- shaped, is supported onthe upper end of an adjustable arm 47 and is adapted to ride to and froon a slide rod 48 under the influence of a screw shaft 49 as it isrotated in either direction by the manipulation of the thumb wheel 37 bythe subscriber. The frame 12 is pro-l vided with a cylindrical boss orhub 50 which is suitably bored to accommodate the screw shaft 49. Ashoulder 51 is fixed to the shaft 49 and abuts the inner edge of the hub50 to prevent the shaft 49 from moving axially to the left when thethumb wheel 37 is rotated. The shank of the thumb wheel abuts the outersurface of the frame 12 and prevents axial movement of the shaft to theright when the thumb wheel is rotated.

The arm 47, near its lower end, is suitably apertured to accommodate theslide bar 48 which is screw-ended for fixing it to the frame. The arm 47also is provided with an internally threaded boss or hub 52 whichaccommodates the threaded end of shaft 49. As the thumb wheel 37 isrotated the shaft 49 rotates and causes the `arm 47 to move laterally onthe rod 48 in one or the other direction depending upon whether thethumb wheel is rotated clockwise or counterclockwise. As the arm 47 isthus moved, the spacing of the permanent magnet 46 relative to thepole-pieces 43 and 45 is increased or decreased.

As the permanent magnet is brought closer to the pole-pieces `themagnetic flux in the gap increases causing an increase in the couplingbetween the clapper rod land the armature. As the magnet is moved awayfrom the pole-pieces the magnetic flux in the gap decreases causing adecrease in the armature-clapper rod coupling. The energy transmitted bythe armature to the clapper rod and, therefore, to the gongs is ameasure of the strength of the armature-clapper rod coupling, whichvaries with variations in the air-gap iiux. Through the thumb wheel 37,screw 49 and arm 47 the ux in the air-gap, and thus the effectivestiffness of the clapper assembly, may be manually controlled by thesubscriber.

Since the energy transmitted to `the clapper determines the force withwhich `the ringer gongs are struck, the sound output of the ringervaries in accordance with the iiux in the air-gap effected by thepole-pieces 43 and 45.

Although two specific embodiments of the invention have been shown anddescribed, it will be understood that they are but illustrative and thatvarious modifica# tions may be made thereon without departing from thescopo and spirit of the invention.

What is claimed is:

1. In a telephone ringer, the combination of a vibratile armature, aclapper rod comprising a pair of magnetical- 1y coupled aligned sectionsarranged in spaced relation, one of said sections fixed to said armatureand bearing a pole-piece, the other of said sections pivotally mountedon said armature and bearing a pole-piece, said polepieces beingrelatively disposed to define an air-gap, and manually operable meansfor adjusting the magnetic cou-Y pling of said sections comprising apermanent magnet and means for variably positioning said permanentmagnet relative to said air-gap.

2. In a telephone ringer, a clapper assembly including a clapper, andmeans operative to move said clapper assembly, said clapper assemblycomprising a clapper-bean ing section pivotally mounted on the operativemeans and in an aligned cooperative relation to `a iixed section alsomounted on the operative means, pole-pieces terminating the cooperatingportions of said sections to effect an air-gap, and means subjectingsaid air-gap to `a magneticux to couple said pole-pieces.

References Cited in the file of this patentY UNITED STATES PATENTS142,486 Little Sept. 2, 1873 1,054,379 Wurster Feb. 25, 1913 1,118,925Erickson Dec. 1, 1914 1,208,096 Cole Dec. 12, 1916 1,744,375 Feder Jan.21, 1930 1,998,537 Edwards Apr. 23, 1935'-

